In recent years, induction heat cooking devices for heating cooking containers such as a pot and a frying pan with a heating coil by induction have been widely used in ordinary households and commercial-use kitchens. The induction heat cooking device includes a heat sensitive element such as a thermistor on a lower surface of a top plate to detect the temperature of the bottom surface of a cooking container with the heat sensitive element, and controls the heating coil so that the detected temperature agrees with a target temperature. For example, when the cooking container is preheated before fried food are cooked, the induction heat cooking device controls the heating coil so that the temperature detected by the heat sensitive element reaches a preheating target temperature.
When a pot contains a large amount of oil and food, for example, when fried food is cooked, (i.e., the load is large), the temperature of the bottom surface of the cooking container gradually increases. In contrast, when a frying pan contains only a small amount of oil (i.e., the load is small), the temperature increases rapidly. In this induction heat cooking device, the heat sensitive element detects the temperature of the bottom surface of the cooking container placed on the top plate by detecting the temperature transferred from the cooking container to the top plate, and therefore, the heat sensitive element has poor temperature following capability with respect to the temperature of the bottom surface of the cooking container. Accordingly, when the temperature of the bottom surface of the cooking container rapidly increases, there is a large error between the actual temperature of the bottom surface of the cooking container and the temperature detected by the heat sensitive element. As a result of this large error, even after the actual temperature of the bottom surface of the cooking container has reached the target temperature, the heat sensitive element cannot detect the actual temperature having reached the target temperature, which causes the induction heat cooking device to continue heating. Therefore, the temperature of the bottom surface of the cooking container may go far beyond the target temperature, and may reach a dangerous temperature such as an oil firing temperature. In order to solve the above problem, a conventional induction heat cooking device detects the temperature gradient of the bottom surface of the cooking container, and stops heating when the temperature gradient is determined to be steeper than a predetermined temperature gradient, thus controlling the heating coil so that the temperature of the bottom surface of the cooking container does not reach a dangerous temperature (for example, refer to Patent Document 1).    Patent Document 1: JP 64-33881 A